Microsatellite instability and defects in mismatch repair proteins: a new aetiology for Sertoli cell-only syndrome

Area of Science:

• Genetics
• Reproductive Biology
• Oncology

Background:

• Microsatellite instability (MSI) is a hallmark of certain cancers and is observed in rodents with DNA mismatch repair (MMR) protein deficiencies.
• Azoospermic mice lacking MMR proteins display spermatogenic defects similar to human testicular failure patients.
• This similarity suggests MSI due to MMR gene deficiencies may be an unrecognized cause of human testicular failure.

Purpose of the Study:

• To investigate the hypothesis that microsatellite instability and DNA mismatch repair defects contribute to human testicular failure.
• To assess the potential for transmission of MMR defects to offspring in azoospermic patients undergoing assisted reproduction.

Main Methods:

• Analysis of microsatellite instability at seven loci in DNA from 41 testicular failure patients and 20 controls.
• DNA extraction from blood and testicular specimens, followed by PCR amplification and fragment length analysis.
• Immunohistochemistry to evaluate the expression of mismatch repair proteins (hMSH2, hMLH1) in patient testicular tissues and fibroblasts.

Main Results:

• Microsatellite instability and DNA mismatch repair protein defects were identified in a subset of azoospermic men.
• These defects were predominantly observed in patients with Sertoli cell-only syndrome (P < 0.01 for MSI, P < 0.05 for MMR defects).

Conclusions:

• Microsatellite instability and DNA mismatch repair defects represent a previously unrecognized etiology for testicular failure in some azoospermic men.
• This finding has implications for understanding male infertility and potential associations with cancer predisposition.